Radio compass system



Nov. 12, 1940. F. J. HOOVEN RADIO coMPAs SYSTEM Original Filed July 16, 1936 a ape/2 22 E INVENTOR. Eeaarz 'rZ'Maaazzz a. ATTORNEY Patented Nov. 12, 1940 2,220,904 ADIO COMPASS SYSTEM Frederick lHoovch, Dayton, Ohio ApplicationJuly 1 1936, Serial No. 90,996

Renewed August 26, 1939 9 Claims My invention relates broadly to radio com-pass "systems and more particularly to an improved circuit arrangement for the visual and audible indication of direction in a radio compass systern. I g

"One of the objects of my invention is toprovide a circuit arrangement for a radio compass system in which directively .propagated beams of high frequency energy may be followed by an aircraft having both audible communication means and visual indicating mechanism with means for preventing mutual interferenceby the simultaneous operation of'both methods of indication.

Another object of my invention is to provide a radio compass system including an oscillator and havin'g a pair of signal channels one of which includes visual indicating'mea'ns and the other or which includes audible communication means l and wherein thecircuits are'designed'to preclude mutual interference during simultaneous operation of both'of said means.

Still another object of my invention is to pro vide a multiple channel indicating system for radio compasses employing an audible frequency localioscillator wherein one ofthe channels operatesa visual indicating system while another :of the channels operates an audible communica- I tion system, the channel connected wtih the vis- 9 ual indicating system'being. principally responsive I tothe oscillator frequency bymeans tuned to the frequency of the oscillator, while the channel which connectswith th audible communication means is responsive to frequencies higher than that of the oscillator frequency.

A further object 'ofm'y' invention is to provide amultiple channelindicator system for radio compasses including both an audibleindicator, and a visual indicator having means for regulat- 40 ing the amplitude of the energy supplied to the indicators in each of said channels.

A still further object of ,my invention is to provide a multiple channel'indicating circuit for a radio compass in which one of the channels v functions to operate an audibl indicator While I another channel operates to control a visual indicator having means in the last mentioned channel for adding any number of visual indicating devices within reasonable limits Without impair- 50 ing the operationof either of the indicatingcham' .nels.

Other and further objects of 1 my invention re side in the circuit arrangement for a radio-compass system asset forth' more fully in the speci- 55 .fication hereinafter following byreference to the radio frequency amplifier tube 2.

'iilandi l'are secondary windings. I r

accompanying draw ng Which diagrammatically illustrates the radio c'ompass systemfof my in vention.

Referring to. the. drawing, reference character i designates the non-directionalantenna'to which i5 the radio receivingv apparatus ofmy invention is connected. The receiving apparatus is construct ed for multi-frequencyoperation. The'non directional receivingapparatusincludesl-rnulti-elecv -'tr'ori'e electron tubes 2 and ii opera'tingas high =10 ireuuency amplifiers, multi-electrodeelectron ube operating asa'converter, multi -electrode elecl trendtubend operating as .an intermediate am- ;6

enter, 'vt'heYdouble-diode' tub -"6 functioningl asl a rectifier, the :multi-electrode electron tube ii -5f functioning as an audio frequency amplifier, and

"the multi-channel audio frequency amplifier" constituted by electron tubes 8 in one channel an'd'fi in another channel.

Referring to the radio requency portion of go. I

the non-directional receiving apparatus it will be seen that tubes 2 and3 are each constituted by a cathode 2d, a-control grid 2b, a shield grid 20, a suppressor grid 2d, and an anode 2e. The corresponding electrodes :have been given small-#25 lar reference characters in thecase'of themultielectrode electron tube 3. Electron tubes r and 9 have their electrodes arranged in a similar manner. I The nonedirectio'nal' -receiving -sys-' V tem is connected with the antenna l and-lground-ao iii through-the tuned circuits i2 and M. The

tunedcircuitsfill and 14 are adjusted to cover different frequency rangesin conjunction with tuning, condenser 15. '-It will be observed that thetuned circuits i 2 and iil are each selectivelyr ,tuned f-or a particular frequency range-by means of trimmer condensers indicated at it and H. Selector switch 18 :controls :the connection :of a selected transformer ortuned circuit il-2 or 14 with v th tuning condenser l-fi'and withtheinputsof j It :will be observed that coils Sand 1.20 are; coupledwith :the'tun'ed circuits [2 and :M and-serve ,asfprimary windings) of .transformeraof which coils.

l Theprimarywindings I'9 and20 areren'dered l selectively: electiveljthroughswitch F21 j'wherby a selected rprimaryrwinding is connected in the output. of thermodulator system constituted by ,pento'd tubes :22 and 23,3111"'thevmodulatorpor- 5 -tion of ;the di1'ectiona1 receiving system which -I have shown generally at 24. The output. F011- cuit of theradiofiifrequency, amplifier :tube

is coupled withthe input -.-circuit of .s radio irewgquency amplifierEtub'e through a transformer ,55

system similar to the transformer system heretofore described and illustrated as constituting sets of coupled windings indicated at 25. and 26, which may be selectively connected in air-- cuit by means of switches 21 and 28 for selectively transmitting the desired frequency through the amplifier system. The sets of transformers coact with tuning condenser 29 in the selective transfer of the desired frequency from one circuit to the other. The output circuit of radio frequency amplifier tube 3 is coupled in a similar manner with the input circuit of converter tube 4, through sets of transformers shown at 38 and 3| which may be selectively connected and rendered effective or ineffective by switches 32 and 33 and which coact with tuning condenser 34 for the transfer of the desired frequency to the circuits of the converter tube It. The converter tube 4 includes the cathode 3a, the control grid 41), the shield grid 40, the anode fie, the oscillator grid 4;, and the oscillator anode grid 4g. Oscillator grid 4 and oscillator anode grid 49 are connected selectively by means of switches 35 and 36 tooscillator coils 37 and 38, which are tuned by means of condenser 39 to a frequency which differs from the received frequency by a fixed amount, called herein the intermediate frequency.

The electron stream of tube 4 is modulated by the oscillator frequency by means of grids 4f and 4g, and by the frequency of the received signal by means of grid 4b. The intermediate frequency then appears in the anode circuit of anode 4e to which is connected transformer 40 which is tuned to the intermediate frequency by means of condensers 4| and 42. The intermediate frequency amplifier constituted bymulti-electrode electron tube 5 transfers theintermediate frequency at increased amplitude through transformer 43 tuned to resonance with the intermediate frequency by means of condensers 44 and 45 to one anode of the double-diode tube 6, as indicated at 46. The rectifier constituted by the set of electrodes in the double-diode tube 6 which includes anode 46 is connected with the input circuit of the audio frequency amplifier 1, whereby rectified energy is impressed on amplifier tube 1, and the rectified and amplified energy is delivered to the inputs of two separate channels as will be hereinafter described. A connection I03 is taken from the rectifier circuit including anode 46 to provide automatically controlled bias potentials for the control grids of tubes 2, 3, 4 and 5 in the non-directional receiving system.

Referring now to the directive portion of the radio compass of my invention illustrated generally at 24, it will be seen that the coil antenna 50 connects through transmission line 5| with the selective coupling system 52. The coupling system 52 constitutes portions which are adapted to transfer signaling energy over the frequency ranges over which the coupling transformers, described in connection with the radio frequency amplifier portion of the non-directional receiving system, operate. One section of the coupling system 52 may comprise the auto-transformer device 53, while another section of the coupling system 52 may comprise the series connected inductance units 54, each adjusted by condensers 55 and '56, respectively. The switches 51 serve to connect the sections 53 and 54 of the coupling system 52 with the transmission line 5| leading to the coil antenna 50. The switches 58 serve to connect the sections of the coupling system with the input circuit of the modulator tubes 22 and 23. The input circuit is tuned by means of condenser 59, operable in unison with the tuning condensers in the non-directional apparatus,

The modulator tubes 22 and 23 are pentagrid tubes, and include, respectively, cathode 22a, control grid 22?), shield grids 22c, suppressor grid 22d, anode 22c, and modulator grid 22 cathode 23a, control grid 23b, shield grids 23c, suppressor grid 23d, anode 23c and modulator grid 23]. The modulator tubes 22 and 23 are supplied with low frequency energy from the local oscillator 60, constituted by pentode tubes 6| and 62. The pentodes 6| and 62, respectively, include the cathode 6|a, control grid 6|b, shield grid Bic, suppressor grid Md, and anode 6 le; cathode 62a, control grid 52b, shield grid 62c, suppressor grid 62d, and anode 62e. The inductance 63 is connected at opposite ends with the control grids fill) and 62b through condensers 64 and 65. The inductance 63 is tapped, as indicated at 66 and 61, for supplying the low frequency energy to the modulator grids 221 and 23 of modulator tubes 22 and 23. Midtap connection 68 is provided on the inductance 63 and connected with the source of positive potential indicated generally at 70. Condenser 69 serves as a tuning means for the inductance 63 in the push-pull oscillator circuit. The feed-back coupling for the push-pull type of oscillator is obtained by the connection through resistor H of shield grid 6|c to that side of coil 63 which is connected to control grid 622). Likewise, shield grid 620 is connected through resistor 12 to that side of coil 63 which is connected to control grid 6|b; the resistors H and 12 constituting a conductive path through coil 63 and center tap 68 to the source of potential ll), and the shield grids (Ho and 620 constituting the anodes of the oscillator system.

It will be seen that the oscillator system is confined to the circuit including the cathode 6|a, control grid (ill), and shield grid 6|c of tube BI, and cathode 620., control grid 62b, and shield grid 620 of tube 62, so that low frequency energy may be drawn from the oscillator by connection to the anodes 6|e and 62e. This connection avoids any tendency of change in frequency of the oscillator under influence of change in load in the indicator circuits, so that the system of my invention is particularly adapted for using two or more indicators without impairing the precision opera tion of the compass. The anode current is supplied to anode 6|e from source of potential 10 through connection 8| and coil 14 of indicator 13. Likewise, the anode current to anode 62c of tube 62 is supplied from the same source through connection 8| and coil 15 of indicator 13. Coils l4 and 15 are so connected that the flux in the magnetic circuit 16 of indicator (3 is proportional to the difference between the currents in coils l4 and 15.

Inspection will reveal that the dynamic poten tial impressed on control grid 61b of tube 6| will be the opposite polarity from that potential impressed on control grid 62b of tube 62 at the same instant. It is thus apparent that the anode There will,

mum power factor for the circuit constituted by coils 14 and 15 and condenser 11, and provides that larger currents of the desired frequency shall flow in these coils and the magnitude of undesired currents of the harmonics of the frequency of j oscillator 60 be reduced. I have shown the indicator 18 similar in all respects to indicator 13 having actuating coils l9 and 80 connected to' anodes tie and 626 and associated with tuning condenser 96. Connection 82, which corresponds to the similar connection 8| of indicator 13, is connected to source of potential 10.

Referring again to the modulator 24 which consists oftubes 22 and 23, the anodes 22c and 236 of tubes 22 and 23 are selectively connected through switch 2| to coils l9 and 20, which are coupled respectively to antenna coils i2 and I4 both inductively and capacitively through condensers 83 and B4. The tubes 22 and 23 are rendered alternately conductive at the frequency of oscillator 551 by means of the modulating grids 22 and 23,. During that part of the cycle of oscillator 66 when modulator grid 22f is positive, modulatorv grid 23 will be negative so that tube 22 will be conductive and tube 23 will be inoper- ,control grids 22b and 2317 are in opposite phase,

7 being connected to the opposite ends of coils 53 or 54, and the anodes 22c and 23e are connected together to output coil l9 or 20, it follows that the phase of the current in output coil I9 or 20 with respect to the phase of the current in coils 53v or E i will be reversed alternately, depending upon the oscillator 60- which determines whether tube22 or tube 23 is conductive.

There will be induced in coil l2 or M a current selected coil by coil l9 or 2B, and the current in .duced therein by the non-directional antenna l. Inasmuch as the current induced in coil i2 or M "by the current in coil 19' or 20 periodicallyreverses its polarity at the frequency of the oscillator 66], it follows that at one instant the current in coil E9 or 20 will tend to add to the current induced in coil'l2 or M by antenna l, and in the other instant will tend to subtract from or oppose the current induced in coil I2 or it by antenna I. The signal impressed on antenna I will, therefore, be'modulated by the, oscillator 60 in pro portion to the voltage impressed on loop antenna 50, and the phase of such modulation with respect to the voltage of oscillator 60 will depend on the phase of the signal impressed on loop antenna 50 with respect to the non-directional antenna i. The combined modulated signal which appears in coil l2 or M is impressed on the nondirectional receiver and amplifier in a manner heretofore described, being demodulated in the circuit including anode 46in double-diode tube 6,

70 1e being connected together to form a common anode. The anode current of tube l is supplied through resistor 85 connected to source of poten tial iii. The audio output of tube 1 is impressed '-by means of condenser 85 on control grid 91) of stube 9, and also by means of condenser 86 and impressed on loop 50.

which [15 the sum of the current induced in the position of these soils being such that thevpomp resistor 81 onto control grid 81) of tube 8 from anode lc-'id'le of control tube 1. i Included in the control grid circuit of tube 8 are coil 88 and condenser 89, constituting the system tuned to, the frequency of oscillator 60. Included in the control grid circuit of tube 9 is resistor 90 whose value is such that its impedance at the frequency of oscillator B ll is low compared with the impedance of condenser 85 at that frequency. Therefore, it will beobserved that the amplifier tube 9 will be rather responsive to frequencies higher than that of oscillator 60, while amplifier tube 8 will be principally responsive to that frequency. The frequency of oscillator 60 is preferably so chosen that its Value is lower than the essential frequencies of speech so that normal voice communication is possible through the audible channel at the'same time the visual indicator is in operation. Tube 8 is a pentode type of tube, includin cathode 8a, control grid 8b, shield grid 80, suppressor grid 8d, and anode fie. The anode lie is connected .to a transformer ti tuned to the freparatus so that these tubes may be rendered inoperative, if desired, for reception through the non-directional system alone. i

We have seen how the signal from antenna l is modulated by the frequency of oscillator 68 in a phase dependingon the phase of the radio signal This modulation is impressed by means already described, on coils 93 and 94 of the indicators l3 and E8, the normal ers of indicators l3 and 18 remain in the center of their respective scales in the absence of phase displacement in the current in coils 93 and 94. The deflection of the pointers of indicators l3 and 18 will, therefore, be in direction and magnitude proportional to the vector product of the currents in actuating coils M and I5 and moving coil d3 of indicator l3, and in actuating coils l9 and 89 and moving coil 9d of indicator 18, when thereis difference in phase in the respective currents in indicators 13 and 18.

tion of the angle of the plane of loop'fifi from a plane normal from the line to the source of the received signal, it follows that the magnitude and direction of the deflection of indicators 13 and' i8 will be a function of the angle of deviation of. v loop from the line to the source of received signal. In order to limit the maximum deflection of the pointers, a control circuit is provided employing the anode ll and associated cathodein the double-diode tube 6. pressed on the anode t? and the cathode, from source it, are such that the diode is conductive when the output current of tube 8 reaches a prenection wt to control the bias potential applied to the control grids in the tubes I22 and 23 in the directional receiving system, the control grids normally receiving bias through connection ill i and resistor 15. The arrangement ofthe visuali'i The potentials imdetermined value, and operative through con- 7 indicators is such that changes in condition of load will not influence the constancy of the oscillator frequency.

The second channel which is connected with the amplifier tube 9 contains the audible indicator device in the output circuit thereof. I have shown the output of amplifier tube 9 connected to the primary winding 9'! of transformer 98 having a secondary winding 99 with a potentiometer iuil connected in shunt therewith. The telephones ID! are connected to an adjustable tap on potentiometer wt for the purpose of determining the volume of the reproduced sound. As heretofore pointed out, the two channels are highly selective in their operation, that is, the channel which includes amplifier 9 contains a condenser and a resistance 96 where the value of the resistance is such that its impedance at the frequency of the oscillator is low compared with the impedance of the condenser 85 at that frequency. As pointed out, the amplifier 9 is designed so that it is responsive to frequencies higher than that of oscillator 69. On the other hand, the channel to which the windings 93 and 54 are connected is tuned to the frequency of the oscillator in resonant circuit 88, 88, and the amplifier 8 is principally responsive to the oscillator frequency. This arrangement provides for the accurate functioning of both the audible channel and the visual signal channel with means for regulating the amplitude of the current output from each of the channels and with means for preventing loading due to operation of the plurality of visual indicators from affecting the frequency of the oscillator.

I have found the circuit arrangement in the system of my invention highly practical and eflicient and successful in operation but I realize that modifications may be made and I intend no limitations upon my invention other than may be imposed by the scope of the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1. In a dynamometer type radio compass system, a directional receiving circuit, a non-directional receiving circuit, means for modulating the energy received in said directional receiving circuit, means for combining said modulated energy with energy from the same source as received by said non-directional receiving circuit, means for demodulating said combined energy, visual and aural signal channels cormected with said demodulating means, said visual signal channel including a dynamometer type indicator having field windings energized from said modulating means, and automatic amplitude control means energized from said visual signal channel and effective in said directional receiving circuit for stabilizing the operation of said modulating means.

2. In a dynamometer type radio compass system, a directional receiving circuit, a non-directional receiving circuit, means for modulating the energy received in said directional receiving circuit, means for combining said modulated energy with energy from the same source as received by said non-directional receiving circuit, means for demodulating said combined energy, visual and aural signal channels connected with said demodulating means, said visual signal channel including a dynamometer type indicator having field windings energized from said modulating means, and means energized from said visual signal channel and effective in said directional receiving circuit for stabilizing the operation of said modulating means.

3. In a radio compass system, a fixed turn rotatable coil antenna, a transmission line connected with said fixed turn rotatable coil antenna, an amplifying and modulating system having input and output circuits, means coupling the end of said transmission line with the input circuit of said amplifying and modulating system comprising separate multifrequency circuits responsive over different frequency ranges, and switching means for selectively rendering one of said circuits effective between the input circuit of said amplifying and modulating system and the end of said transmission line while isolating the others of said circuits.

4. In a radio compass system, a fixed turn rotatable coil antenna, a transmission line connected with said fixed turn rotatable coil antenna, a balanced modulator having input and output circuits, means coupling the end of said transmission line with the input circuit of said balanced modulator comprising separate multifrequency circuits responsive over different frequency ranges, one of said circuits including a parallel resonant system and another of said circuits including a series resonant system, and switching means for selectively rendering one of said circuits effective between the input circuit of the balanced modulator and the end of said transmission line while isolating the others of said circuits.

5. In a radio compass system, a fixed turn rotatable coil antenna, a transmission line connected with said fixed turn rotatable coil antenna, a balanced modulator having input and output circuits, means coupling the end of said transmission line with the input circuit of said balanced modulator comprising separate multifrequency circuits responsive over different frequency ranges, one of said circuits including an inductance shunted by an adjustable condenser and another of said circuits including separate series connected inductances, each connectible at their input ends with the coil antenna and connected at their output ends by an adjustable condenser, and switching means for selectively rendering one of said circuits effective between the input circuit of the balanced modulator and the end of said transmission line while isolating the others of said circuits.

6. In a radio compass system, a fixed turn rotatable coil antenna, a transmission line connected with said fixed turn rotatable coil antenna, a balanced modulator having input and output circuits, means coupling the end of said transmission line with the input circuit of said balanced modulator comprising separate multifrequency circuits responsive over different frequency ranges, one of said circuits including an inductance shunted by an adjustable condenser with taps on said inductance connectible withv said coil antenna and another of said circuits including a pair of inductances connectible in series with the transmission line and having adjustable condensers connected across the ends thereof remote from the transmission line, and switching means for selectively rendering one of said circuits effective between the input circuit of the balanced modulator and the end of said transmission line while isolating the others of said circuits.

7. In a radio compass system, a fixed turn rotatable coil antenna, a transmission line connected with said fixed turn rotatable coil antenna, a balanced modulator having input and output circuits, means coupling the end of said transmission line with'the input circuit of said balanced modulator comprising separate multifrequency circuits responsive over different frequency ranges, one of said circuits including an inductance, an adjustable impedance connectible in shunt with the transmission line and another of said circuits including a pair of inductances connectible in series with the transmission line and to an adjustable impedance, variable tuning means connected across the input circuit of said balanced modulator, and switching means for selectively rendering one of said circuits effective between the input circuit of the balanced modulater and the end of said transmission line while isolating the others of said circuits. 8. In aradio compass system, a non-directional receiving'circuit, a signal receiving system conf nected with said non-directional receiving circuit, separate coupling circuits for said signal receiving system responsive over different frequency ranges, a directional receiving circuit, an amplifying and modulating system, separate coupling circuits disposed between said directional receiving circuit and said amplifying and modulating system, and responsive over different frequency ranges, switchingmeans for simultaneously and selectively completing'the circuits between certain of the coupling circuits in said signal receiving system and said non-directional receiving circuit and certain of the coupling means be-,

tween the directional receiving circuit and said amplifying and modulating system, means for combining the modulated energy With energy received by the non-directional receiving circuit, means for demodulating the combined energy,

and means for observing the effects of the combined energy.

9 Ina radio compass system, a non-directional electrically adjusting each of said separate coupling circuits, switching means for selectively completing-the circuits between the non-directional receiving circuit and certain of the coupling circuits in said signal receiving system, separate switching means for completing the circuits between ,saiddirectional receiving circuit and certain of. the coupling means between the directional receiving circuit and said amplifying and modu lating system, tuning means connected with said amplifying and modulating system and tunable throughout the range of either of the separate coupling circuits coupled therewith, means for combining the modulated energy with energy received by'the non-directional receiving circuit, "means for demodulating the combined energy, and means for observing the effects of the com-' bined energy.

FREDERICK J. HOO'VEN. 

